Preheat your oven to 350°F (175°C). In a 9x13-inch baking pan, prepare the white or vanilla cake mix according to the package directions. Pour the batter into the pan and spread it evenly. Bake for about 25-30 minutes, until golden brown.

Remove the cake from the oven and allow it to cool for 10–15 minutes in the pan.

Using the handle of a wooden spoon, poke holes evenly across the surface of the cooled cake.

In a mixing bowl, dissolve your flavored gelatin in 2 cups of boiling water, stirring vigorously until fully dissolved. Then add 1 cup of cold water.

Gradually pour the gelatin mixture over the cake, ensuring it seeps into the holes.

Cover the cake with plastic wrap and refrigerate for at least 3 hours or overnight.

For the optional topping, whip together heavy whipping cream, powdered sugar, and vanilla extract until soft peaks form.

Spread the whipped cream over the top of the cake. Slice into squares and serve chilled.